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- 2018 (58) (remove)
Management strategies for sustainable sugarcane production need to deal with the increasing complexity and variability of the whole sugar system. Moreover, they need to accommodate the multiple goals of different industry sectors and the wider community. Traditional disciplinary approaches are unable to provide integrated management solutions, and an approach based on whole systems analysis is essential to bring about beneficial change to industry and the community. The application of this approach to water management, environmental management and cane supply management is outlined, where the literature indicates that the application of extreme learning machine (ELM) has never been explored in this realm. Consequently, the leading objective of the current research was set to filling this gap by applying ELM to launch swift and accurate model for crop production data-driven. The key learning has been the need for innovation both in the technical aspects of system function underpinned by modelling of sugarcane growth. Therefore, the current study is an attempt to establish an integrate model using ELM to predict the concluding growth amount of sugarcane. Prediction results were evaluated and further compared with artificial neural network (ANN) and genetic programming models. Accuracy of the ELM model is calculated using the statistics indicators of Root Means Square Error (RMSE), Pearson Coefficient (r), and Coefficient of Determination (R2) with promising results of 0.8, 0.47, and 0.89, respectively. The results also show better generalization ability in addition to faster learning curve. Thus, proficiency of the ELM for supplementary work on advancement of prediction model for sugarcane growth was approved with promising results.
Polymer-modified cement concrete (PCC) is a heterogeneous building material with a hierarchically organized microstructure. Therefore, continuum micromechanics-based multiscale models represent a promising method to estimate the mechanical properties. By means of a bottom-up approach, homogenized properties at the macroscopic scale are derived considering microstructural characteristics. The extension of existing multiscale models for the application to PCC is the main objective of this work. For that, cross-scale experimental studies are required. Both macroscopic and microscopic mechanical tests are performed to characterize the elastic and viscoelastic properties of different PCC. The comparison between experiment and model prediction illustrates the success of the modeling approach.
Polymeric nanocomposites (PNCs) are considered for numerous nanotechnology such as: nano-biotechnology, nano-systems, nanoelectronics, and nano-structured materials. Commonly , they are formed by polymer (epoxy) matrix reinforced with a nanosized filler. The addition of rigid nanofillers to the epoxy matrix has offered great improvements in the fracture toughness without sacrificing other important thermo-mechanical properties. The physics of the fracture in PNCs is rather complicated and is influenced by different parameters. The presence of uncertainty in the predicted output is expected as a result of stochastic variance in the factors affecting the fracture mechanism. Consequently, evaluating the improved fracture toughness in PNCs is a challenging problem.
Artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) have been employed to predict the fracture energy of polymer/particle nanocomposites. The ANN and ANFIS models were constructed, trained, and tested based on a collection of 115 experimental datasets gathered from the literature. The performance evaluation indices of the developed ANN and ANFIS showed relatively small error, with high coefficients of determination (R2), and low root mean square error and mean absolute percentage error.
In the framework for uncertainty quantification of PNCs, a sensitivity analysis (SA) has been conducted to examine the influence of uncertain input parameters on the fracture toughness of polymer/clay nanocomposites (PNCs). The phase-field approach is employed to predict the macroscopic properties of the composite considering six uncertain input parameters. The efficiency, robustness, and repeatability are compared and evaluated comprehensively for five different SA methods.
The Bayesian method is applied to develop a methodology in order to evaluate the performance of different analytical models used in predicting the fracture toughness of polymeric particles nanocomposites. The developed method have considered the model and parameters uncertainties based on different reference data (experimental measurements) gained from the literature. Three analytical models differing in theory and assumptions were examined. The coefficients of variation of the model predictions to the measurements are calculated using the approximated optimal parameter sets. Then, the model selection probability is obtained with respect to the different reference data.
Stochastic finite element modeling is implemented to predict the fracture toughness of polymer/particle nanocomposites. For this purpose, 2D finite element model containing an epoxy matrix and rigid nanoparticles surrounded by an interphase zone is generated. The crack propagation is simulated by the cohesive segments method and phantom nodes. Considering the uncertainties in the input parameters, a polynomial chaos expansion (PCE) surrogate model is construed followed by a sensitivity analysis.
Increasing structural robustness is the goal which is of interest for structural engineering community. The partial collapse of RC buildings is subject of this dissertation. Understanding the robustness of RC buildings will guide the development of safer structures against abnormal loading scenarios such as; explosions, earthquakes, fine, and/or long-term accumulation effects leading to deterioration or fatigue. Any of these may result in local immediate structural damage, that can propagate to the rest of the structure causing what is known by the disproportionate collapse.
This work handels collapse propagation through various analytical approaches which simplifies the mechanical description of damaged reinfoced concrete structures due to extreme acidental event.
Die hier vorliegende Arbeit befasst sich mit dem Modifizieren von Computerspielen (Modding). Die Annäherung an das Modding geschieht aus zwei unterschiedlichen Blickrichtungen: Zum einen wird mit einem analytischen Blick auf das Themenfeld geschaut, der das bereits Erforschte mit den eigenen Suchbewegungen kombiniert. Zum anderen wird die Perspektive der Handlung eingenommen, die sich in der Widerständigkeit des Materials, der Werkzeuge und der Spieltechnologie äußert. Im Mittelpunkt der Auseinandersetzung stehen das Modding als Praxis, die Mods als Derivate und die Erforschung des Computerspiels mit den Praktiken und Derivaten des Modifizierens. Das Modding wird so zu einer epistemischen Praxis des Computerspiels.
Die hier formulierten Überlegungen zum Modding, als eine forschende Praxis des Computerspiels, präsentieren eine Vorgehensweise, die ästhetische, widerständige und stabilisierende Aspekte in sich vereint. Sie dient der Erforschung des Computerspiels entlang seiner Diskussionen, Materialien, Technologien und Praktiken und fokussiert hierbei auf das Abseitige, dass als integraler Bestandteil des Computerspiels verstanden wird. Mit diesem Blick auf die Grenzen des Computerspielens werden Dinge sichtbar, die zwar Teil der synthetischen Computerspielwelten sind, durch dessen Inszenierungen und Atmosphären jedoch verschleiert werden. Der hier entwickelte Ansatz ermöglicht einen Perspektivenwechsel innerhalb dieser Welten und die Erforschung des Computerspiels unter besonderer Berücksichtigung seiner eingeschriebenen Normen und Machtverhältnissen. Das Modding dient hierbei als eine kritische Praxis zur Entschlüsselung dieser medial vermittelten Konstellationen.
This cumulative dissertation discusses - by the example of four subsequent publications - the various layers of a tangible interaction framework, which has been developed in conjunction with an electronic musical instrument with a tabletop tangible user interface. Based on the experiences that have been collected during the design and implementation of that particular musical application, this research mainly concentrates on the definition of a general-purpose abstraction model for the encapsulation of physical interface components that are commonly employed in the context of an interactive surface environment. Along with a detailed description of the underlying abstraction model, this dissertation also describes an actual implementation in the form of a detailed protocol syntax, which constitutes the common element of a distributed architecture for the construction of surface-based tangible user interfaces. The initial implementation of the presented abstraction model within an actual application toolkit is comprised of the TUIO protocol and the related computer-vision based object and multi-touch tracking software reacTIVision, along with its principal application within the Reactable synthesizer. The dissertation concludes with an evaluation and extension of the initial TUIO model, by presenting TUIO2 - a next generation abstraction model designed for a more comprehensive range of tangible interaction platforms and related application scenarios.
Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses.
The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity.
The accurate representation of aerodynamic forces is essential for a safe, yet reasonable design of long-span bridges subjected to wind effects. In this paper, a novel extension of the Pseudo-three-dimensional Vortex Particle Method (Pseudo-3D VPM) is presented for Computational Fluid Dynamics (CFD) buffeting analysis of line-like structures. This extension entails an introduction of free-stream turbulent fluctuations, based on the velocity-based turbulence generation. The aerodynamic response of a long-span bridge is obtained by subjecting the 3D dynamic representation of the structure to correlated free-stream turbulence in two-dimensional (2D) fluid planes, which are positioned along the bridge deck. The span-wise correlation of the free-stream turbulence between the 2D fluid planes is established based on Taylor's hypothesis of frozen turbulence. Moreover, the application of the laminar Pseudo-3D VPM is extended to a multimode flutter analysis. Finally, the structural response from the Pseudo-3D flutter and buffeting analyses is verified with the response, computed using the semi-analytical linear unsteady model in the time-domain. Meaningful merits of the turbulent Pseudo-3D VPM with respect to the linear unsteady model are the consideration of the 2D aerodynamic nonlinearity, nonlinear fluid memory, vortex shedding and local non-stationary turbulence effects in the aerodynamic forces. The good agreement of the responses for the two models in the 3D analyses demonstrates the applicability of the Pseudo-3D VPM for aeroelastic analyses of line-like structures under turbulent and laminar free-stream conditions.
The need for finding persuasive arguments can arise in a variety of domains such as politics, finance, marketing or personal entertainment. In these domains, there is a demand to make decisions by oneself or to convince somebody about a specific topic. To obtain a conclusion, one has to search thoroughly different sources in literature and on the web to compare various arguments. Voice interfaces, in form of smartphone applications or smart speakers, present the user with natural conversations in a comfortable way to make search requests in contrast to a traditional search interface with keyboard and display. Benefits and obstacles of such a new interface are analyzed by conducting two studies. The first one consists of a survey for analyzing the target group with questions about situations, motivations, and possible demanding features. The latter one is a wizard-of-oz experiment to investigate possible queries on how a user formulates requests to such a novel system. The results indicate that a search interface with conversational abilities can build a helpful assistant, but to satisfy the demands of a broader audience some additional information retrieval and visualization features need to be implemented.
Entwicklung und Untersuchung von alternativen Dicalciumsilicat-Bindern auf der Basis von alpha-C2SH
(2018)
Um den Klimawandel zu begrenzen, müssen die CO2-Emissionen drastisch gesenkt werden [100]. Bis 2050 soll bei der Herstellung von Zement eine Einsparung um 51–60 % auf 0,425–0,350 tCO2/tZement erfolgen [7]. Um dieses Ziel zu erreichen, sind alternative Bindemittelkonzepte notwendig [70].
Diese Arbeit widmet sich alternativen, hochreaktiven Dicalciumsilicat-Bindemitteln, die durch die thermische Aktivierung von α-Dicalcium-Silicat-Hydrat (α-C2SH) erzeugt werden. Das α-C2SH ist eine kristalline C S H-Phase, die im hydrothermalen Prozess, beispielsweise aus Branntkalk und Quarz, herstellbar ist. Die thermische Aktivierung kann bei sehr niedrigen Temperaturen erfolgen (>420 °C) und führt zu einem Multiphasen-C2S-Binder. Als besonders reaktive Bestandteile können x-C2S und röntgenamorphe Anteile enthalten sein. Weiterhin können β C2S, γ C2S und Dellait (Ca6(SiO4)(Si2O7)(OH)2) entstehen.
Im Rahmen der Arbeit wird zunächst der Stand des Wissens zur Polymorphie und Hydratation von C2S zusammengefasst. Es werden bekannte C2S-basierte Bindemittelkonzepte vorgestellt und bewertet.
Die Herstellung von C2S-Bindern wird experimentell im Labormaßstab untersucht. Dabei kommen unterschiedliche Autoklaven und ein Muffelofen zum Einsatz. Die Herstellungsparameter werden hinsichtlich Phasenbestand und Reaktivität optimiert. Die Bindemittel werden durch quantitative Röntgen-Phasenanalyse (QXRD), Rasterelektronenmikroskopie (REM), N2-Adsorption (BET-Methode), Heliumpycnometer, Thermoanalyse (TGA/DSC) und 29Si-MAS- sowie 29Si-1H-CP/MAS-NMR-Spektroskopie charakterisiert. Das Hydratationsverhalten der Bindemittel wird vorrangig mithilfe von Wärmeflusskalorimetrie untersucht. Weiterhin werden in situ und ex situ XRD-, TGA/DSC- und REM-Untersuchungen durchgeführt. Anhand von zwei Bindemitteln wird die Fähigkeit zur Erzielung hoher Festigkeiten demonstriert. Abschließend erfolgt eine Abschätzung zu Energiebedarf und CO2-Emissionen für die Herstellung der untersuchten C2S-Binder.
Die Ergebnisse zeigen, dass für eine hohe Reaktivität der Binder eine niedrige Brenntemperatur und ein geringer Wasserdampfpartialdruck während der thermischen Aktivierung entscheidend sind. Weiterhin muss das hydrothermal hergestellte α-C2SH eine möglichst hohe spezifische Oberfläche aufweisen. Diese Parameter beeinflussen den Phasenbestand und die phasenspezifische Reaktivität. Brenntemperaturen von ca. 420–500 °C führen zu hochreaktiven Bindern, die im Rahmen dieser Arbeit als Niedertemperatur-C2S-Binder bezeichnet werden. Temperaturen von ca. 600–800 °C führen zu Bindern mit geringerer Reaktivität, die im Rahmen dieser Arbeit als Hochtemperatur-C2S bezeichnet werden. Höhere Brenntemperaturen (1000 °C) führen zu Bindemitteln, die innerhalb der ersten drei Tage keine hydraulische Aktivität zeigen.
Die untersuchten Bindemittel können sehr hohe Reaktionsgeschwindigkeiten erreichen. Die Wärmeflusskalorimetrie deutet bei einigen Bindemitteln einen nahezu vollständigen Umsatz innerhalb von drei Tagen an. Durch XRD wurde für einen Binder der vollständige Verbrauch von x-C2S innerhalb von drei Tagen nachgewiesen. Für einen mittels in-situ-XRD und Wärmeflusskalorimetrie untersuchten Binder wurde gezeigt, dass die Phasen vorrangig in der Reihenfolge röntgenamorph > x-C2S > β-C2S > γ-C2S hydratisieren. Hydratationsprodukte sind nadelige C S H-Phasen und Portlandit.
Die Herstellung durch thermische Aktivierung von α-C2SH führt zu tafeligen Bindemittelpartikeln, die teilweise Zwickelräume und Poren zwischen den einzelnen Partikeln einschließen. Um eine verarbeitbare Bindemittelpaste zu erzeugen, sind daher sehr hohe Wasser/Bindemittel-Werte (z. B. 1,4) erforderlich. Der Wasseranspruch kann durch Mahlung etwa auf das Niveau von Zement gesenkt werden.
Die Druckfestigkeitsentwicklung wurde an zwei Niedertemperatur-C2S-Kompositbindern mit 40 % Kalksteinmehl bzw. 40 % Hüttensand untersucht. Aufgrund von theoretischen Betrachtungen zur Porosität in Abhängigkeit des w/b-Wertes wurde dieser auf 0,3 festgelegt. Durch Zugabe von PCE-Fließmittel wurde ein verarbeitbarer Mörtel erhalten. Die Festigkeitsentwicklung ist sehr schnell. Der Kalksteinmehl-Binder erreichte nach zwei Tagen 46 N/mm². Bis Tag 28 trat keine weitere Festigkeitssteigerung ein. Der Hüttensand-Binder erreichte nach zwei Tagen 62 N/mm². Durch die Hüttensandreaktion stieg die Festigkeit bis auf 85 N/mm² nach 28 Tagen an.
Für den Herstellungsprozess von Niedertemperatur-C2S-Binder wurden Energieverbräuche und CO2-Emissionen abgeschätzt. Es deutet sich an, dass, bezogen auf die Bindemittelmenge, keine wesentlichen Einsparungen im Vergleich zur Portlandzementherstellung möglich sind. Für die tatsächlichen Emissionen muss jedoch zusätzlich die Leistungsfähigkeit der Bindemittel berücksichtigt werden. Die Leistungsfähigkeit kann als erforderliche Bindemittelmenge betrachtet werden, die je m³ Beton eingesetzt werden muss, um bestimmte Festigkeits-, Dauerhaftigkeits- und Verarbeitungseigenschaften zu erreichen.
Aus verschiedenen Veröffentlichungen [94, 201, 206] wurde die These abgeleitet, dass die Leistungsfähigkeit eines Bindemittels maßgeblich von der C-S-H-Menge bestimmt wird, die während der Hydratation gebildet wird. Daher wird für NT-C2S-Binder eine außergewöhnlich hohe Leistungsfähigkeit erwartet.
Auf Basis der Leistungsfähigkeitsthese verringern sich die abgeschätzten CO2-Emissionen von NT-C2S-Bindern, sodass gegenüber Portlandzement ein mögliches Einsparpotenzial von 42 % ermittelt wurde.
Die Thesis untersucht am Beispiel von Farb-Licht Forschungen (Interaktion dynamischen Lichts mit farbigen Oberflächen) und der Designforschungen am Potenzial der organisch Licht emittierenden Dioden (OLED) integrierende Aspekte des Designs im Kontext dieser Technologien. Des weiteren reflektiert die Thesis am Beispiel dieser Designforschungen das Verhältnis von Designforschung und Innovation für die gestalterischen Disziplinen.
Keine Ahnung? Landschaft!
(2018)
... soll auf den folgenden Seiten eine dritte Richtung angedeutet und vorgezeichnet werden, die ebenso Interesse am Erkenntnisgewinn durch das Thema Landschaft bekundet, dies hingegen aus der Umkehrung heraus erreichen will. Dreht man den Richtungspfeil, stehen wir ihr, der Landschaft, gegenüber. Vom Modus des Aktiven geraten wir in die Passivität. Damit wird eine Korrektur der Fragestellung möglich. Es entsteht eine Perspektive, die die Überlegungen zulässt: Was die Landschaft eigentlich mit uns macht?, welchen Horizont sie uns eröffnet und entstehen lässt, welche Bedeutung und welche Qualität wir dem ›Landschaftlichen‹ zuschreiben können, worin die Notwendigkeit ihres Erhalts und der Nutzen für die gegenwärtige Gesellschaft bestehen kann.
Following restructuring of power industry, electricity supply to end-use customers has undergone fundamental changes. In the restructured power system, some of the responsibilities of the vertically integrated distribution companies have been assigned to network managers and retailers. Under the new situation, retailers are in charge of providing electrical energy to electricity consumers who have already signed contract with them. Retailers usually provide the required energy at a variable price, from wholesale electricity markets, forward contracts with energy producers, or distributed energy generators, and sell it at a fixed retail price to its clients. Different strategies are implemented by retailers to reduce the potential financial losses and risks associated with the uncertain nature of wholesale spot electricity market prices and electrical load of the consumers. In this paper, the strategic behavior of retailers in implementing forward contracts, distributed energy sources, and demand-response programs with the aim of increasing their profit and reducing their risk, while keeping their retail prices as low as possible, is investigated. For this purpose, risk management problem of the retailer companies collaborating with wholesale electricity markets, is modeled through bi-level programming approach and a comprehensive framework for retail electricity pricing, considering customers’ constraints, is provided in this paper. In the first level of the proposed bi-level optimization problem, the retailer maximizes its expected profit for a given risk level of profit variability, while in the second level, the customers minimize their consumption costs. The proposed programming problem is modeled as Mixed Integer programming (MIP) problem and can be efficiently solved using available commercial solvers. The simulation results on a test case approve the effectiveness of the proposed demand-response program based on dynamic pricing approach on reducing the retailer’s risk and increasing its profit.
In this paper, the decision-making problem of the retailers under dynamic pricing approach for demand response integration have been investigated. The retailer was supposed to rely on forward contracts, DGs, and spot electricity market to supply the required active and reactive power of its customers. To verify the effectiveness of the proposed model, four schemes for retailer’s scheduling problem are considered and the resulted profit under each scheme are analyzed and compared. The simulation results on a test case indicate that providing more options for the retailer to buy the required power of its customers and increase its flexibility in buying energy from spot electricity market reduces the retailers’ risk and increases its profit. From the customers’ perspective also the retailers’accesstodifferentpowersupplysourcesmayleadtoareductionintheretailelectricityprices. Since the retailer would be able to decrease its electricity selling price to the customers without losing its profitability, with the aim of attracting more customers. Inthiswork,theconditionalvalueatrisk(CVaR)measureisusedforconsideringandquantifying riskinthedecision-makingproblems. Amongallthepossibleoptioninfrontoftheretailertooptimize its profit and risk, demand response programs are the most beneficial option for both retailer and its customers. The simulation results on the case study prove that implementing dynamic pricing approach on retail electricity prices to integrate demand response programs can successfully provoke customers to shift their flexible demand from peak-load hours to mid-load and low-load hours. Comparing the simulation results of the third and fourth schemes evidences the impact of DRPs and customers’ load shifting on the reduction of retailer’s risk, as well as the reduction of retailer’s payment to contract holders, DG owners, and spot electricity market. Furthermore, the numerical results imply on the potential of reducing average retail prices up to 8%, under demand response activation. Consequently, it provides a win–win solution for both retailer and its customers.
We proposed two different time-dependent modeling approaches for variation of device characteristics of perovskite solar cells under stress conditions. The first approach follows Sah-Noyce-Shockley (SNS) model based on Shockley–Read–Hall recombination/generation across the depletion width of pn junction and the second approach is based on thermionic emission model for Schottky diodes. The connecting point of these approaches to time variation is the time-dependent defect generation in depletion width (W) of the junction. We have fitted the two models with experimental data reported in the literature to perovskite solar cell and found out that each model has a superior explanation for degradation of device metrics e.g. current density and efficiency by time under stress conditions. Nevertheless, the Sah-Noyce-Shockley model is more reliable than thermionic emission at least for solar cells.
Biodiesel, as the main alternative fuel to diesel fuel which is produced from renewable and available resources, improves the engine emissions during combustion in diesel engines. In this study, the biodiesel is produced initially from waste cooking oil (WCO). The fuel samples are applied in a diesel engine and the engine performance has been considered from the viewpoint of exergy and energy approaches. Engine tests are performed at a constant 1500 rpm speed with various loads and fuel samples. The obtained experimental data are also applied to develop an artificial neural network (ANN) model. Response surface methodology (RSM) is employed to optimize the exergy and energy efficiencies. Based on the results of the energy analysis, optimal engine performance is obtained at 80% of full load in presence of B10 and B20 fuels. However, based on the exergy analysis results, optimal engine performance is obtained at 80% of full load in presence of B90 and B100 fuels. The optimum values of exergy and energy efficiencies are in the range of 25–30% of full load, which is the same as the calculated range obtained from mathematical modeling.
A Hybrid Clustering and Classification Technique for Forecasting Short-Term Energy Consumption
(2018)
Electrical energy distributor companies in Iran have to announce their energy demand at least three 3-day ahead of the market opening. Therefore, an accurate load estimation is highly crucial. This research invoked methodology based on CRISP data mining and used SVM, ANN, and CBA-ANN-SVM (a novel hybrid model of clustering with both widely used ANN and SVM) to predict short-term electrical energy demand of Bandarabbas. In previous studies, researchers introduced few effective parameters with no reasonable error about Bandarabbas power consumption. In this research we tried to recognize all efficient parameters and with the use of CBA-ANN-SVM model, the rate of error has been minimized. After consulting with experts in the field of power consumption and plotting daily power consumption for each week, this research showed that official holidays and weekends have impact on the power consumption. When the weather gets warmer, the consumption of electrical energy increases due to turning on electrical air conditioner. Also, con-sumption patterns in warm and cold months are different. Analyzing power consumption of the same month for different years had shown high similarity in power consumption patterns. Factors with high impact on power consumption were identified and statistical methods were utilized to prove their impacts. Using SVM, ANN and CBA-ANN-SVM, the model was built. Sine the proposed method (CBA-ANN-SVM) has low MAPE 5 1.474 (4 clusters) and MAPE 5 1.297 (3 clusters) in comparison with SVM (MAPE 5 2.015) and ANN (MAPE 5 1.790), this model was selected as the final model. The final model has the benefits from both models and the benefits of clustering. Clustering algorithm with discovering data structure, divides data into several clusters based on similarities and differences between them. Because data inside each cluster are more similar than entire data, modeling in each cluster will present better results. For future research, we suggest using fuzzy methods and genetic algorithm or a hybrid of both to forecast each cluster. It is also possible to use fuzzy methods or genetic algorithms or a hybrid of both without using clustering. It is issued that such models will produce better and more accurate results.
This paper presents a hybrid approach to predict the electric energy usage of weather-sensitive loads. The presented methodutilizes the clustering paradigm along with ANN and SVMapproaches for accurate short-term prediction of electric energyusage, using weather data. Since the methodology beinginvoked in this research is based on CRISP data mining, datapreparation has received a gr eat deal of attention in thisresear ch. Once data pre-processing was done, the underlyingpattern of electric energy consumption was extracted by themeans of machine learning methods to precisely forecast short-term energy consumption. The proposed approach (CBA-ANN-SVM) was applied to real load data and resulting higher accu-racy comparing to the existing models.
2018 American Institute of Chemical Engineers Environ Prog, 2018
https://doi.org/10.1002/ep.12934
Für den Frost-Tausalz-Angriff auf Beton existiert eine Reihe von Schadenstheorien. Drei aktuelle Theorien nehmen für sich in Anspruch, den Schadensmechanismus und insbesondere den Einfluss niedrig konzentrierter Tausalzlösungen auf den Schädigungsgrad gut abbilden zu können. Die Glue Spall-Theorie sowie die Cryogenic Suction-Theorie bieten plausible Ansätze. In Untersuchungen konnten einige Modellvorstellungen bestätigt werden, insbesondere der Prozess des kryogenen Saugens. Ob dieser Vorgang oder die mechanische Glue Spall-Belastung tatsächlich schadensauslösend sind, kann anhand der Untersuchungen jedoch noch nicht zweifelsfrei bestätigt oder ausgeschlossen werden. Die Brine Rejection-Theorie zeigt wichtige Prozesse auf, die für die Schädigung bei einem Frost-Tausalz-Angriff relevant sein können. Als alleinstehendes Modell ist es eher nicht geeignet.
Over the past few decades, the increasing demands of railways operations in the form of heavy loading and high speed have been noticed. Railway formation and ballast deform progressive under heavy axle cyclic loading, therefore the rail track needs proper design of ballast and formation bed to achieve the desire stiffness and stability for the safe and sound serviceability of the track. For the overall stability of the track on soft formation, the ground is improved by different techniques prior to the construction on that, in order to avoid the failure and differential settlement during the designed trains operation.
The numerical analyses illustrate that the total deformation and bearing capacity of the railway tracks mostly depend on the changes in the friction angle and cohesion of the selected soils of the subgrade. To avoid failure in the formation of track under the design loads, the proper selection of types of soils, its layer thickness, well compaction during construction and provision of proper track drainage system are extremely important. For the construction of new railway tracks the soils having greater values of friction angle, cohesion and elastic stiffness with the well graded ballast cushion under the sleepers of designed side slopes can be used to reduce the maintenance cost, considerably increase the life time of the components of the tracks and ultimately give better performance of the tracks.
Bei einem marktüblichen Calciumsulfat-Fließestrich wurden in der Praxis schädigende Volu-menexpansionen festgestellt. Diese sind ein Resultat aus dem Zusammenwirken des einge-setzten Bindemittel-Compounds und einer kritischen Gesteinskörnung.
Das Ziel dieser Arbeit ist es, ein Calciumsulfat-Bindemittelsystem zu konfektionieren, welches in der Lage ist, die im Mörtel festgestellten Volumenexpansionen zu unterbinden. Es sollen verschiedene Bindemittel- und Additivzusammensetzungen untersucht werden, welche in Verbindung mit der kritischen Gesteinskörnung die Herstellung eines volumenstabilen Fließestrichs ermöglichen. Dazu soll folgende Fragestellung beantwortet werden: Welche Ursachen hat die Volumenzunahme und wie ist diese zu minimieren bzw. unterbinden?
Dabei werden unterschiedliche Bindemittelrezepturen aus α-Halbhydrat, Thermoanhydrit und Naturanhydrit, sowie verschiedene Additivzusammensetzungen hergestellt und untersucht.
Durch Längenänderungsmessungen in der Schwindrinne werden die Einflüsse der Binde-mittel, der Additivzusammensetzungen und der Wasser/Bindemittel-Werte auf das Län-genänderungsverhalten untersucht. Mittels Variation der einzelnen Compound-Bestandteile kann festgestellt werden, dass der Stabilisierer die Längenänderung negativ beeinflusst. Dieser bindet freies Wasser, welches für eine Reaktion zwischen Bindemittel und Gesteins-körnung im plastischen Zustand nicht mehr zur Verfügung steht. Diese Reaktion kann folglich erst im erhärteten Zustand ablaufen und verursacht die schädigende Volumenexpansion.
Abschließend wurde ein Bindemittel-Compound konfektioniert, welcher ohne Zusatz von Stabilisierern in Zusammenhang mit der kritischen Gesteinskörnung volumenstabil ist und keine Schäden auslöst.
In this work, molecular separation of aqueous-organic was simulated by using combined soft computing-mechanistic approaches. The considered separation system was a microporous membrane contactor for separation of benzoic acid from water by contacting with an organic phase containing extractor molecules. Indeed, extractive separation is carried out using membrane technology where complex of solute-organic is formed at the interface. The main focus was to develop a simulation methodology for prediction of concentration distribution of solute (benzoic acid) in the feed side of the membrane system, as the removal efficiency of the system is determined by concentration distribution of the solute in the feed channel. The pattern of Adaptive Neuro-Fuzzy Inference System (ANFIS) was optimized by finding the optimum membership function, learning percentage, and a number of rules. The ANFIS was trained using the extracted data from the CFD simulation of the membrane system. The comparisons between the predicted concentration distribution by ANFIS and CFD data revealed that the optimized ANFIS pattern can be used as a predictive tool for simulation of the process. The R2 of higher than 0.99 was obtained for the optimized ANFIS model. The main privilege of the developed methodology is its very low computational time for simulation of the system and can be used as a rigorous simulation tool for understanding and design of membrane-based systems.
Highlights are, Molecular separation using microporous membranes. Developing hybrid model based on ANFIS-CFD for the separation process, Optimization of ANFIS structure for prediction of separation process
Ziel der Arbeit war das Adsorptionsverhalten ausgewählter schutzkolloidstabilisierter Polymerpartikel mit variierender chemischer Basis im zementären System zu beschreiben und basierend auf den gewonnenen Erkenntnissen das Konkurrenzverhalten beim Angebot unterschiedlicher mineralischer Oberflächen zu klären.
Sowohl die Destabilisierung der Polymerpartikel im alkalischen Milieu, welche eine Voraussetzung für derartige Adsorptionsprozesse ist, als auch die Veränderung von Oberflächeneigenschaften verschiedener mineralischer Partikel durch Hydratations- und Ionenadsorptionsprozesse, wurden u. a. mit Hilfe elektrokinetischer Experimente erfasst. Die spektralphotometrische Erstellung von Adsorptionsisothermen ermöglichte zudem die Ermittlung der jeweiligen adsorbierten Polymermenge zu verschiedenen Zeitpunkten der frühen Hydratation. Weiterhin wurde die Polymeradsorption an Partikeln ausgewählter Zusatzstoffe in Abhängigkeit von der Ionenstärke der Flüssigphase beschrieben.
Rasterelektronenmikroskopische Untersuchungen cryo-präparierter polymermodifizierter Zementleimproben ermöglichten es außerdem deren Mikrostruktur im suspensiven Zustand zu visualisieren. Diese Aufnahmen, ebenso wie die Ergebnisse grundlegender hydratationskinetischer Untersuchungen wurden in Wechselbeziehung zu den Ergebnissen der Adsorptionsuntersuchungen gebracht.
Maßgelbliche intermolekulare und interpartikuläre Wechselwirkungen, infolge derer sich die Stabilitätsverhältnisse im Zementleim ändern und die Polymerpartikel adsorbieren sind im Wesentlichen die Desorption des Schutzkolloids von der Polymerpartikeloberfläche, die Ionisation funktioneller Gruppen der Polymerpartikel und der Schutzkolloidmakromoleküle im alkalischen Milieu und infolgedessen die Komplexbildung mit Ionen der Zementleimporenlösung. Die Auswirkungen dieser Vorgänge auf die Lösungs- und Fällungskinetik des Zementleimes wurden erfasst und mit der chemischen Zusammensetzung der polymeren Systeme korreliert.
In computer-aided design (CAD), industrial products are designed using a virtual 3D model. A CAD model typically consists of curves and surfaces in a parametric representation, in most cases, non-uniform rational B-splines (NURBS). The same representation is also used for the analysis, optimization and presentation of the model. In each phase of this process, different visualizations are required to provide an appropriate user feedback. Designers work with illustrative and realistic renderings, engineers need a
comprehensible visualization of the simulation results, and usability studies or product presentations benefit from using a 3D display. However, the interactive visualization of NURBS models and corresponding physical simulations is a challenging task because of the computational complexity and the limited graphics hardware support.
This thesis proposes four novel rendering approaches that improve the interactive visualization of CAD models and their analysis. The presented algorithms exploit latest graphics hardware capabilities to advance the state-of-the-art in terms of quality, efficiency and performance. In particular, two approaches describe the direct rendering of the parametric representation without precomputed approximations and timeconsuming pre-processing steps. New data structures and algorithms are presented for the efficient partition, classification, tessellation, and rendering of trimmed NURBS surfaces as well as the first direct isosurface ray-casting approach for NURBS-based isogeometric analysis. The other two approaches introduce the versatile concept of programmable order-independent semi-transparency for the illustrative and comprehensible visualization of depth-complex CAD models, and a novel method for the hybrid reprojection of opaque and semi-transparent image information to accelerate stereoscopic rendering. Both approaches are also applicable to standard polygonal geometry which contributes to the computer graphics and virtual reality research communities.
The evaluation is based on real-world NURBS-based models and simulation data. The results show that rendering can be performed directly on the underlying parametric representation with interactive frame rates and subpixel-precise image results. The computational costs of additional visualization effects, such as semi-transparency and stereoscopic rendering, are reduced to maintain interactive frame rates. The benefit of this performance gain was confirmed by quantitative measurements and a pilot user study.
Living heritage sites are strongly connected to their historical, geographical, socio-political and cultural context. A descriptive narrative of the evolutionary process of the living heritage site of a Sufi shrine is undertaken in this research. It focuses on the changing relationship between the spatial and socio-cultural aspects over time. The larger or macro regional context is interrelated to the micro architectural context. The tangible heritage is defined by and intimately tied to the intangible aspects of the heritage. It is these constituting macro and micro elements and their interrelationships particularly through space and architecture that the research thesis explores in its documentation and analysis.
The Sufi shrine in the South Asian Pakistani context is representative of a larger culture in the precolonial era. It is an expression of an indigenous modernity, belonging to a certain time period, place and community. The Sufi shrine as a building type has evolved from the precolonial time period, particularly starting at the golden ages of the Muslim Empire in the world (9th – 12th century), through the colonial age when western modernity arrived until the current neoliberal paradigm within the post independence period. Continued and evolved use of space, ritualistic performances, multiple social groups using the site are various elements whose documentation and analysis can establish the essential co-relations that contribute to continuity of its historical living. Physical and social relation of the historic site to its immediate settlement context is also a significant element that preserves the socio-cultural context.
The chosen case of the Shrine of Shah Abdul Latif Bhitai, situated in the small town of Bhitshah in the province of Sindh, Pakistan forms a unique example where the particular physical and socio-cultural environment forms the context within which the Sufi heritage lives and survives. It is well integrated within its context at multiple levels. What are these levels and how do the constituting elements integrate is a major subject of research? These form the background to defining some of the basic issues and questions addressed in this doctoral thesis.
Given that living heritage sites are unique due to their particular association to the context, the case study method was used to gain deeper insight and understanding on the topic.
As part of an international research project – funded by the European Union – capillary glasses for facades are being developed exploiting storage energy by means of fluids flowing through the capillaries. To meet highest visual demands, acrylate adhesives and EVA films are tested as possible bonding materials for the glass setup. Especially non-destructive methods (visual analysis, analysis of birefringent properties and computed tomographic data) are applied to evaluate failure patterns as well as the long-term behavior considering climatic influences. The experimental investigations are presented after different loading periods, providing information of failure developments. In addition, detailed information and scientific findings on the application of computed tomographic analyses are presented.
Components of structural glazing have to meet different requirements and resist various impacts, depending on the field of application. Within an international research project of the EU innovation program Horizon 2020, special glass panes with a fluid circulating in capillaries are developed exploiting solar energy. Major influences to this glazing are UV irradiation and the fluidic contact, effecting the mechanical and optical durability of the bonding material within the glass setup. Regarding to visual requirements, acrylate adhesives and EVA films are analyzed as possible bonding materials by destructive and non-destructive testing methods. Two types of specimen are presented for obtaining the mechanical behavior and the surface appearances of the bonding material.
This dissertation concerns the changing role of fashion in the context of modern cities. In approaching this process, the research investigates the media discourse based on representations of fashion by cities and of cities by fashion. Moreover, this research focuses on fashion understood as a multidimensional phenomenon that aims to provide an explanation of urban spaces through fashion terms, actions, and garments. Additionally, cities are considered from the cultural geography approach that highlights the cultural component of urban spaces expressed in social and cultural practices in physical reality. Following this idea, it is suggested here that fashion today not only participates in the urban life as its significant component but also creates city images and representations of urban lifestyle through the fashion paradigm. In other words, fashion redefines urban spaces; at the same time, urban spaces are interpreted as a stage for fashion processes.
By integrating in social research the fields of urban studies and fashion studies, this dissertation offers the discussion considering the fashion phenomenon not only as an urban phenomenon of modern reality. On the one hand, such discussion concerns the re-conceptualization of urban phenomena by the fashion influence; on the other hand, it relates the re-contextualization of fashion in a city. The empirical focus is based on the media context of fashion magazines in which variety of possibilities to represent fashion and cities lead to promising interpretations and analysis. The idea of representation specifies the ways of constructing the notion of urban space as fashionable space and the notion of fashion as placed in the urban context.
In the field of engineering, surrogate models are commonly used for approximating the behavior of a physical phenomenon in order to reduce the computational costs. Generally, a surrogate model is created based on a set of training data, where a typical method for the statistical design is the Latin hypercube sampling (LHS). Even though a space filling distribution of the training data is reached, the sampling process takes no information on the underlying behavior of the physical phenomenon into account and new data cannot be sampled in the same distribution if the approximation quality is not sufficient. Therefore, in this study we present a novel adaptive sampling method based on a specific surrogate model, the least-squares support vector regresson. The adaptive sampling method generates training data based on the uncertainty in local prognosis capabilities of the surrogate model - areas of higher uncertainty require more sample data. The approach offers a cost efficient calculation due to the properties of the least-squares support vector regression. The opportunities of the adaptive sampling method are proven in comparison with the LHS on different analytical examples. Furthermore, the adaptive sampling method is applied to the calculation of global sensitivity values according to Sobol, where it shows faster convergence than the LHS method. With the applications in this paper it is shown that the presented adaptive sampling method improves the estimation of global sensitivity values, hence reducing the overall computational costs visibly.
Im Rahmen der Dissertation ist ein analytisches Berechnungsverfahren zur Ermittlung der Kapazität in lichtsignalgeregelten Zufahrten mit zusätzlichen Aufstellstreifen bei gleichzeitiger Freigabezeit entwickelt worden, dass sich durch folgende Eigenschaften auszeichnet:
a) einfaches Berechnungsverfahren – Ansatz eines einfachen linearen Berechnungsansatzes, der auf den Grundzusammenhängen des Verkehrsablaufs in lichtsignalgeregelten Zufahrten aufbaut,
b) breites Anwendungsgebiet – Berechnungsverfahren kann in Zufahrten mit bis zu zwei zusätzlichen Aufstellstreifen angewendet werden,
c) hohe Genauigkeit – Im Rahmen eines direkten Vergleichs konnte u. a.
gezeigt werden, dass mit dem hergeleiteten analytischen Berechnungsverfahren genauere Kapazitätswerte ermittelt werden können, als mit dem Berechnungsverfahren nach HBS 2015.
Die späten 1960er Jahre und vor allem die 1970er Jahre waren eine Hochphase der Mieter_innenproteste in der BRD. Dieser Beitrag verfolgt die These, dass die Krise der fordistischen Wohnraumversorgung in den 1960er Jahren, bzw. die von der Politik implementierten Lösungsstrategien dieser Krise, eine Klassenallianz in wohnungsbezogenen Protesten ermöglichte und, dass sich diese Klassenallianz im Laufe der 1970er und 1980er Jahre aufspaltete, was zur Einhegung des Protests in das entstehende neoliberale Projekt führte. Im Folgenden beschreibe ich also zunächst die Wohnungsfrage 1968 als Krise der fordistischen Wohnraumproduktion und damit die materielle Basis der Klassenallianz. Daran anschließend illustriere ich anhand von Protesten in den drei Bereichen Massenwohnungsbau, Sanierungsgebiete und Hausbesetzungen die Klassenallianz und vollziehe ich deren Aufspaltung nach. Und schließlich stelle ich die Frage, was heute aus dieser Geschichte gelernt werden kann.
This dissertation is devoted to the theoretical development and experimental laboratory verification of a new damage localization method: The state projection estimation error (SP2E). This method is based on the subspace identification of mechanical structures, Krein space based H-infinity estimation and oblique projections. To explain method SP2E, several theories are discussed and laboratory experiments have been conducted and analysed.
A fundamental approach of structural dynamics is outlined first by explaining mechanical systems based on first principles. Following that, a fundamentally different approach, subspace identification, is comprehensively explained. While both theories, first principle and subspace identification based mechanical systems, may be seen as widespread methods, barely known and new techniques follow up. Therefore, the indefinite quadratic estimation theory is explained. Based on a Popov function approach, this leads to the Krein space based H-infinity theory. Subsequently, a new method for damage identification, namely SP2E, is proposed. Here, the introduction of a difference process, the analysis by its average process power and the application of oblique projections is discussed in depth.
Finally, the new method is verified in laboratory experiments. Therefore, the identification of a laboratory structure at Leipzig University of Applied Sciences is elaborated. Then structural alterations are experimentally applied, which were localized by SP2E afterwards. In the end four experimental sensitivity studies are shown and discussed. For each measurement series the structural alteration was increased, which was successfully tracked by SP2E. The experimental results are plausible and in accordance with the developed theories. By repeating these experiments, the applicability of SP2E for damage localization is experimentally proven.
This study aims to develop an approach to couple a computational fluid dynamics (CFD) solver to the University of California, Berkeley (UCB) thermal comfort model to accurately evaluate thermal comfort. The coupling was made using an iterative JavaScript to automatically transfer data for each individual segment of the human body back and forth between the CFD solver and the UCB model until reaching convergence defined by a stopping criterion. The location from which data are transferred to the UCB model was determined using a new approach based on the temperature difference between subsequent points on the temperature profile curve in the vicinity of the body surface. This approach was used because the microclimate surrounding the human body differs in thickness depending on the body segment and the surrounding environment. To accurately simulate the thermal environment, the numerical model was validated beforehand using experimental data collected in a climate chamber equipped with a thermal manikin. Furthermore, an example of the practical implementations of this coupling is reported in this paper through radiant floor cooling simulation cases, in which overall and local thermal sensation and comfort were investigated using the coupled UCB model.
Advances in nanotechnology lead to the development of nano-electro-mechanical systems (NEMS) such as nanomechanical resonators with ultra-high resonant frequencies. The ultra-high-frequency resonators have recently received significant attention for wide-ranging applications such as molecular separation, molecular transportation, ultra-high sensitive sensing, high-frequency signal processing, and biological imaging. It is well known that for micrometer length scale, first-principles technique, the most accurate approach, poses serious limitations for comparisons with experimental studies. For such larger size, classical molecular dynamics (MD) simulations are desirable, which require interatomic potentials. Additionally, a mesoscale method such as the coarse-grained (CG) method is another useful method to support simulations for even larger system sizes.
Furthermore, quasi-two-dimensional (Q2D) materials have attracted intensive research interest due to their many novel properties over the past decades. However, the energy dissipation mechanisms of nanomechanical resonators based on several Q2D materials are still unknown. In this work, the addressed main issues include the development of the CG models for molybdenum disulphide (MoS2), investigation of the mechanism effects on black phosphorus (BP) nanoresonators and the application of graphene nanoresonators. The primary coverage and results of the dissertation are as follows:
Method development. Firstly, a two-dimensional (2D) CG model for single layer MoS2 (SLMoS2) is analytically developed. The Stillinger-Weber (SW) potential for this 2D CG model is further parametrized, in which all SW geometrical parameters are determined analytically according to the equilibrium condition for each individual potential term, while the SW energy parameters are derived analytically based on the valence force field model. Next, the 2D CG model is further simplified to one-dimensional (1D) CG model, which describes the 2D SLMoS2 structure using a 1D chain model. This 1D CG model is applied to investigate the relaxed configuration and the resonant oscillation of the folded SLMoS2. Owning to the simplicity nature of the 1D CG model, the relaxed configuration of the folded SLMoS2 is determined analytically, and the resonant oscillation frequency is derived analytically. Considering the increasing interest in studying the properties of other 2D layered materials, and in particular those in the semiconducting transition metal dichalcogenide class like MoS2, the CG models proposed in current work provide valuable simulation approaches.
Mechanism understanding. Two energy dissipation mechanisms of BP nanoresonators are focused exclusively, i.e. mechanical strain effects and defect effects (including vacancy and oxidation). Vacancy defect is intrinsic damping factor for the quality (Q)-factor, while mechanical strain and oxidation are extrinsic damping factors. Intrinsic dissipation (induced by thermal vibrations) in BP resonators (BPRs) is firstly investigated. Specifically, classical MD simulations are performed to examine the temperature dependence for the Q-factor of the single layer BPR (SLBPR) along the armchair and zigzag directions, where two-step fitting procedure is used to extract the frequency and Q-factor from the kinetic energy time history. The Q-factors of BPRs are evaluated through comparison with those of graphene and MoS2 nanoresonators. Next, effects of mechanical strain, vacancy and oxidation on BP nanoresonators are investigated in turn. Considering the increasing interest in studying the properties of BP, and in particular the lack of theoretical study for the BPRs, the results in current work provide a useful reference.
Application. A novel application for graphene nanoresonators, using them to self-assemble small nanostructures such as water chains, is proposed. All of the underlying physics enabling this phenomenon is elucidated. In particular, by drawing inspiration from macroscale self-assembly using the higher order resonant modes of Chladni plates, classical MD simulations are used to investigate the self-assembly of water molecules using
graphene nanoresonators. An analytic formula for the critical resonant frequency based on the interaction between water molecules and graphene is provided. Furthermore, the properties of the water chains assembled by the graphene nanoresonators are studied.
The Local Governance of Arrival in Leipzig: Housing of Asylum-Seeking Persons as a Contested Field
(2018)
The article examines how the German city of Leipzig governs the housing of asylum seekers. Leipzig was a frontrunner in organizing the decentralized accommodation of asylum seekers when adopting its accommodation concept in 2012. This concept aimed at integrating asylum-seeking persons in the regular housing market at an early stage of arrival. However, since then, the city of Leipzig faces more and more challenges in implementing the concept. This is particularly due to the increasingly tight situation on the housing market while the number of people seeking protection increased and partly due to discriminating and xenophobic attitudes on the side of house owners and managers. Therefore, we argue that the so-called refugee crisis of 2015–2016 has to be seen in close interaction with a growing general housing shortage in Leipzig like in many other large European cities. Furthermore, we understand the municipal governing of housing as a contested field regarding its entanglement of diverse federal levels and policy scales, the diversity of stakeholders involved, and its dynamic change over the last years. We analyze this contested field set against the current context of arrival and dynamic urban growth on a local level. Based on empirical qualitative research that was conducted by us in 2016, Leipzig’s local specifics will be investigated under the umbrella of our conceptual framework of Governance of Arrival. The issues of a strained housing market and the integration of asylum seekers in it do not apply only to Leipzig, but shed light on similar developments in other European Cities.
The Variability of the Void Ratio of Sand and its Effect on Settlement and Infinite Slope Stability
(2018)
The uncertainty of a soil property can significantly affect the physical behavior of soil, so as to influence geotechnical practice. The uncertainty can be expressed by its stochastic parameters, including the mean, the standard deviation, and the spatial correlation length. These stochastic parameters are regarded as constant value in most of the former studies. The main aim of this thesis is to prove whether they are depth-dependent, and to evaluate the effect of this depth-dependent character on both the settlement and the infinite slope stability during rainwater infiltration.
A stochastic one-dimensional settlement simulation is carried out using random finite element method with the von Wolffersdorff hypoplastic model, so as to evaluate the effect of stress level on the stochastic parameters of void ratio related parameters of sand. It is found that these stochastic parameters are both stress-dependent and depth-dependent.
The non-stationary random field, considering the depth-dependent character of these stochastic parameters, can be generated through the distortion of the stationary random field.
The one-dimensional settlement analysis is carried out to evaluation the effect of the depth-dependent character of the stochastic parameters of void ratio on the strain. It is found that the depth-dependent character has low effect on the strain.
The deterministic analysis of infinite slope stability during rainwater infiltration is simulated.
The transient seepage is carried out using finite difference method, while the steady state seepage is simulated using the analytical solution. The saturated hydraulic conductivity (ks) is taken as the only variable. The results show that the depth-dependent ks has a significant influence on the stability of the slope when the negative flux is high. Without considering the depth-dependent character, can overestimate the factor of safety of the slope. A slope can fail if the depth-dependent character is considered, while it is stable if the depth-dependent character is neglected. The failure time of the slope with a greater depth-dependent ks is earlier during transient infiltration.
Meanwhile, the stochastic infinite slope stability analysis during infiltration, is also carried out to highlight the effect of the depth-dependent character of the stochastic parameters of ks. The results show that: the probability of failure is significantly increased if the depth-dependent character of mean is considered, while, it is moderately reduced if the depth-dependent character of the standard deviation is accounted. If the depth-dependent character of both the mean and standard deviation of ks is considered, the depth-dependent mean value plays a dominant influence on the results. Furthermore, the depth-dependent character of the spatial correlation length can slightly reduce the probability of failure.